1. Field of the Invention
The present invention relates to a signaling safety system for a transit system moving on a track, such as railroads, monorails, and LRT (light rail transit: next generation streetcar). More particularly, the invention provides a signaling safety system that is operable when each train approaches a specific range, using radio communication devices that are installed respectively on the ground and train. When ground communication by radio cannot be used, the invention provides for switching from operation via ground-train radio communication to the operation by additional communication devices.
2. Description of the Related Art
In a conventional railroad signaling safety system, train detectors called track circuits are installed on all tracks and are used to confirm the presence of a train on-rail. However, installation expenses of track circuits and maintenance expenses are enormous, so that a railroad system in which the need for track circuits is eliminated is currently sought. One system that is being considered, for example, detects the presence of a train on-rail and performs train control by the ground-train communication by radio, with each train confirming its own position by integrating the number of revolutions of the axle, and notifying the management section on the ground. Thus the ground side manages the positions of all trains.
However, to cancel an error in position calculation by the integral value of the number of revolutions of the axle, on the ground, balises having position information are installed as required, and when a train passes each balise, the position information from the balise is received by the train, thus an error in position calculation is canceled periodically, and correct position information can be obtained. According to this system, on each train, a radio communication means may be installed, and on the ground side, a radio communication base station may be installed, and furthermore in necessary portions on the track, balises for position correction may be installed, and track circuits are completely abolished. Thus the installation and maintenance expenses can be cut down greatly.
Meanwhile, in Patent Document 1, even when an error is caused in a cable communication route generally used and failure information generated in the system cannot be notified to the outside of the system via the cable communication route, the cable communication route is connected to a radio communication network as a backup communication route, thus the failure information can be notified to the outside of the system. Further, in Patent Document 2, without using rails or a loop antenna, transponder balises transmit a restricted speed signal or an incoming possibility discrimination signal to a car.
Patent Document 1: Japanese Application Patent Laid-Open Publication No. 2002-247035
Patent Document 2: Japanese Application Patent Laid-Open Publication No. 2003-11819